Waveform calculators are often used in conjunction with waveform analyzers in the aerospace and electronics industries in order to design and test the behavior of electrical circuits. The waveform calculator may be used to create, view, edit, or perform mathematical operations on signals. The waveform analyzer is then used to fine tune, test, scale or simulate the waveform for the specific needs of the user.
Current waveform calculators provide the user with a user interface for entering expressions, an expression-entry window, and a results window. The user interface usually provides buttons or keys in order to enter numerals, variables, equations, operations, etc. The expression-entry window displays the entered expression, and the results window displays the result of the computation done by the calculator using the expressions entered by the user.
Due to the nature of circuit design and testing, a user often must input numerous expressions, perform numerous computations, and view numerous results while using a waveform calculator. The numerous results, computations and expressions become cumbersome and difficult to organize on current waveform calculators because of the scrolling design of current results windows and limitations on the amount of display area that can be used for displaying information. Users must scroll through numerous results to find a desired result and often do not recall what operation or what expressions were used to obtain that result. These problems force a user to make many repetitive expression entries and calculations that would be unnecessary with a more effective and efficient method of displaying the calculator usage history.